[PATCH] drm/amd/display: Allow spatial dither to 10 bpc on all != DCE-11.0.

[Alex Deucher]

On Fri, Feb 12, 2021 at 5:30 PM Mario Kleiner
<mario.kleiner.de at gmail.com> wrote:
>
> Spatial dithering to 10 bpc depth was disabled for all DCE's.
> Restrict this to DCE-11.0, but allow it on other DCE's.
>
> Testing on DCE-8.3 and DCE-11.2 did not show any obvious ill
> effects, but a measureable precision improvement (via colorimeter)
> when displaying a fp16 framebuffer to a 10 bpc DP or HDMI connected
> HDR-10 monitor.
>
> Alex suggests this may have been a workaround for some DCE-11.0
> Carrizo and Stoney Asics, so lets try to restrict this to DCE 11.0.
>
> Signed-off-by: Mario Kleiner <mario.kleiner.de at gmail.com>
> Cc: Alex Deucher <alexdeucher at gmail.com>
> ---
>  drivers/gpu/drm/amd/display/dc/dce/dce_opp.c | 9 ++++++---
>  1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/display/dc/dce/dce_opp.c b/drivers/gpu/drm/amd/display/dc/dce/dce_opp.c
> index 4600231da6cb..4ed886cdb8d8 100644
> --- a/drivers/gpu/drm/amd/display/dc/dce/dce_opp.c
> +++ b/drivers/gpu/drm/amd/display/dc/dce/dce_opp.c
> @@ -216,9 +216,12 @@ static void set_spatial_dither(
>         REG_UPDATE(FMT_BIT_DEPTH_CONTROL,
>                 FMT_TEMPORAL_DITHER_EN, 0);
>
> -       /* no 10bpc on DCE11*/
> -       if (params->flags.SPATIAL_DITHER_ENABLED == 0 ||
> -               params->flags.SPATIAL_DITHER_DEPTH == 2)
> +       if (params->flags.SPATIAL_DITHER_ENABLED == 0)
> +               return;
> +
> +       /* No dithering to 10 bpc on DCE-11.0 */
> +       if (params->flags.SPATIAL_DITHER_DEPTH == 2 &&
> +               opp110->base.ctx->dce_version == DCE_VERSION_11_0)
>                 return;

I'm inclined to just remove this check altogether.  This is just the
dithering control.  I think the limitations are more around the
formats (e.g., FP formats) than the dithering.

Alex


>
>         /* only use FRAME_COUNTER_MAX if frameRandom == 1*/
> --
> 2.25.1
>